When applying a coating such as ink, paint, or varnish for example, to a substrate, it is typically important that the coating be adequately adhered to the surface of the substrate to which it is applied. This is especially important in industries such as printing, painting, and converting related industries. During the manufacturing process in these types of industries, many factors can affect the adhesive strength of the bond between the inks, paints, and other coatings, and the surface of the substrate. Thus, it is necessary to test the adhesion during the manufacturing/printing/painting/converting process to confirm that a desired level of adhesion is obtained. A standard test, commonly termed a tape test and described in ASTM test standards D3359 and F1842, as well as other test standards such as ISO 2409, for example, has been developed for evaluating the adhesive strength of the bond between the inks, paints, and coatings and the surface of the substrate.
The tape test is performed by applying a strip of tape to the coated surface, removing it, and visually evaluating the amount of coating that has been removed by the tape. In the standard test, the tape is both applied and removed by hand. In cases where the coating has ingredients that create a slick or difficult to bond surface, the surface can be prepared by cutting through or “cross-hatching” the coating in a criss-cross pattern with a sharp knife edge. It is generally accepted in the printing, painting, and converting industries that the adhesion of the coating to the surface of the substrate can be evaluated employing the tape test.
In the course of performing and observing thousands of tape tests, the inventors have determined that the human controlled motions in the tape test have a significant impact on the final results. The variability of these human motions can produce widely varying results from test specimens that would otherwise be observed as having a substantially equivalent bond strength. For example, if the tape is applied to the coated surface with the palm of a hand for one test, with a thumb in another test, with a pencil eraser in another (as suggested in some standards), and with a fingernail or other solid surface in yet another test, each application method may create a different bond strength between the adhesive of the tape and the surface being evaluated, resulting in different results from each test.
Additionally, the rate at which the tape is removed from the surface being tested and the angle at which the tape is pulled in respect of its applied position are known to significantly influence the results of the test. The referenced ASTM standards suggest pulling the tape off 180 degrees from itself rapidly (not jerked). However, this method is not always followed by a person performing the test.
The strength of the bond between the coating and the surface of the substrate is frequently incorrectly reported as a result of the variability in the hand application and the hand removal of the tape. This may cause the printer/ manufacturer to either make adjustments to the process of applying the coating when none are needed, or fail to recognize when adjustments to the process are needed. In either case, unreliable or unrepeatable results from the tape test may create costly manufacturing errors.
It would be desirable to provide a device that facilitates consistently applying a tape to and removing the tape from a coated surface of a substrate to evaluate the adhesive strength of the bond between the coating and the substrate.